Electrode holder assemblies are often seen in chemical laboratories and other locations where it is necessary to perform either qualitative or quantitative analyses on various sample solutions or substances. The assemblies are used to support one or more test probes or electrodes that are immersed in a sample of a substance in order to obtain a desired analytic test parameter from the substance. An example of such probes is a pH meter test electrode that is used to find the H+ ion concentration of a sample.
A probe holder assembly usually has a probe holder platform or bracket through which the electrode is inserted so to bring it into contact with the test samples. Typically, the platform has a mounting bore, or slot, through which the electrode is inserted. The electrode is held in the mounting bore by cap on the probe that has a diameter larger than the bore, or by a thumb-screw clamp that extends into the bore to fasten the electrode. Alternatively, the tip of the electrode rests on the bottom of the container for the test sample, in which case the platform provides only lateral support for the probe.
Each of these arrangements has disadvantages. For example, electrodes having caps that rest on the top of the holder platform are not height-adjustable. Thus, if electrodes of different heights are simultaneously used with the same supporting platform the sensor elements of the probe will be at different vertical positions. Thus one probe may rest on the bottom of the sample container, while the tip of another probe may be above the top of the sample.
Thumb screw mechanisms permit height adjustment of the probes relative to the platforms. However, they pose a breakage problem when delicate probes are used.
There are also disadvantages to having the bottom tip of the electrode rest in the sample container. For example, it would interface with the operation of a magnetic stirring bar in the bottom of the container. Most importantly, in many test electrodes the actual sensor element or membrane is located at the bottom tip of the electrode, and having that tip in contact with the bottom of the sample container will interfere with proper functioning of the electrode.
A need therefore exists for a new improved retainer for supporting a probe on a probe holder platform so that the probe can be supported in any desired position relative to the platform. The retainer should also accommodate electrodes of varied diameter, and can be easily used without posing a probe breakage problem.